Liquified gas in cylinders or "bottles" is commonly used on mobile homes, recreational vehicles and boats as a source of fuel gas for heating and cooking. Where liquid petroleum gas is required on boats, there is usually provided some sort of metal, gas-tight box or the like in which the gas cylinder must be kept to prevent escape of gases within the vessel. Then, an exhaust or vent duct must be provided to extend outside of the boat above the waterline. Since the venting system relies on gravity the gas bottle must also be above the waterline and, on many vessels there are few convenient places to locate the gas-tight box. It would be highly desirable to have a containment system that could by design be placed anywhere aboard the vessel or vehicle without requiring a special bin or other enclosure.